Laberintectomía quirúrgica e implante coclear simultáneo en paciente con enfermedad de Ménière bilateral / Simultaneous labyrinthectomy with cochlear implantation in a patient with bilateral Ménière's disease

Los pacientes con enfermedad de Ménière representan un desafío terapéutico para el médico tratante, especialmente cuando no responden al tratamiento médico conservador. Presentamos un caso de un paciente de 45 años con enfermedad de Ménière activa en oído izquierdo sometido a laberintectomía quirúrgica con implante coclear simultáneo en dicho oído. Se evaluaron resultados clínicos y audiométricos en un seguimiento de 9 meses posencendido del implante y el paciente presentó PTP de 21 dB, con 92% de discriminación a disílabos a 45 dB en el oído implantado, sin tinnitus ni síntomas vestibulares. La combinación de laberintectomía con implante coclear en un mismo tiempo quirúrgico, fue efectiva en controlar los síntomas vestibulares y audiológicos del paciente estudiado.

Patients with Méniére's disease represent a therapeutical problem for physicians, especially in those who do not respond to conservative approaches. We report the case of a 45-year-old male with bilateral Ménière's disease, active in the left ear, who underwent simultaneous cochlear implantation combined with labyrinthectomy surgery. Audiometric and clinical results were evaluated, 9 months after the activation of the implant the patient's PTA was 21 dB, with 92% disyllabic word's discrimination at 45 dB in the implanted ear, without tinnitus or vestibular symptoms. The combined surgical labyrinthectomy and cochlear implantation are efficient for the treatment of vestibular and audiological symptoms of the patient.

Laberintectomía quirúrgica / Surgical labyrinthectomy

El tratamiento quirúrgico del vértigo se puede dividir en dos grandes grupos: no ablativos y ablativos, dentro de éstos últimos se encuentra la laberintectomía quirúrgica, técnica con la cual se produce cofosis. Su principal indicación es la sintomatología vestibular periférica invalidante, unilateral, que no mejora con medidas farmacológicas ni con terapia psiquiátrica, asociado a hipoacusia sensorioneural severa a profunda. Existen dos tipos de abordajes para realizar la laberintectomía quirúrgica: transmastoidea y transcanal, siendo la primera el gold standard para eliminar la función vestibular. Se presentarán dos casos clínicos de pacientes sometidos a estos procedimientos, uno por vía transmastoidea y otro por vía transcanal.

The surgical treatment of vertigo can be classified into two main groups: non-ablative and ablative. The surgical labyrinthectomy is an ablative treatment in which no hearing is preserved. Its main indication is the disabling peripherical and unilateral vestibular symptoms that do not improve with pharmacological measures or with psychiatric therapy, in patients with severe to profound sensorineural hearing loss. There are two types of approaches for labyrinthectomy, transmastoid and transcanal, the first is the gold standard to eliminate the vestibular function. Here, we present two cases of patients undergoing these procedures, one by transmastoid approach and the other by transcanal approach.

Reduction of long-term potentiation at Schaffer collateral-CA1 synapses in the rat hippocampus at the acute stage of vestibular compensation

Vestibular compensation is a recovery process from vestibular symptoms over time after unilateral loss of peripheral vestibular end organs. The aim of the present study was to observe time-dependent changes in long-term potentiation (LTP) at Schaffer collateral-CA1 synapses in the CA1 area of the hippocampus during vestibular compensation. The input-output (I/O) relationships of fEPSP amplitudes and LTP induced by theta burst stimulation to Schaffer's collateral commissural fibers were evaluated from the CA1 area of hippocampal slices at 1 day, 1 week, and 1 month after unilateral labyrinthectomy (UL). The I/O relationships of fEPSPs in the CA1 area was significantly reduced within 1 week post-op and then showed a non-significant reduction at 1 month after UL. Compared with sham-operated animals, there was a significant reduction of LTP induction in the hippocampus at 1 day and 1 week after UL. However, LTP induction levels in the CA1 area of the hippocampus also returned to those of sham-operated animals 1 month following UL. These data suggest that unilateral injury of the peripheral vestibular end organs results in a transient deficit in synaptic plasticity in the CA1 hippocampal area at acute stages of vestibular compensation.

Hearing Preservation with the Transcrusal Approach to the Skull Base Lesion Combined with Other Transcranial Approach: Results of Consecutive Series of 5 Cases / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: This study reviewed our experience and outcomes of surgery via transcrusal approach to the skull base lesions. SUBJECTS AND METHOD: We performed transcrusal approach technique on five patients with skull base lesions (Cavernous malformation, Petroclival meningioma, Craniopharyngioma, Anaplastic astrocytoma, and Trigerminal epidermoid cyst) aiming at preserving hearing. Pre-and post-operative pure tone audiometry (PTA) and caloric test were performed in all patients. The transcrusal approach technique was performed as reported in the previous references. The approach included trephination of the superior and posterior semicircular canals from the ampullae to the common crus. The main outcome of this study was preserving hearing and the vestibular function after surgery, which was determined by PTA and caloric test. RESULTS: The average diameter of skull base lesion of the five patients was 3.68 cm. The mean follow up period was 114.2 days. The pre-operative mean PTA of five patients was 11 dB. The mean PTA of five patients within seven days after surgery was 28 dB. The last measured mean PTA was 29.8 dB. The pre and post-operative caloric results measured revealed vestibular function deficit in all of the patients after surgery (mean decreased value: 64%). All patients were stable during the surgery. Complications included two cerebrospinal fluid leak (40%) and one cranial VI nerve deficit (20%). CONCLUSION: Transcrusal approach is a method that can simultaneously preserve hearing and afford enough exposure of the skull base lesion if appropriately combined with other transcranial approach. We performed transcrusal approach targeting skull base lesion with hearing preservation, and we found excellent hearing result with this technique.

Role of the Cerebral Cortex on Vestibular Compensation Following Unilateral Labyrinthectomy in Rats / 대한평형의학회지

OBJECTIVE: The cerebral cortex can modulate vestibular functions through direct control of neuronal activities in the vestibular nuclei. The purpose of this study was to investigate the effect of unilateral cortical lesion or cortical stimulation on static vestibular symptoms and vestibular nuclear activities at the acute stage of vestibular compensation following unilateral labyrinthectomy (UL) in rats. METHODS: The photothrombic ischemic injury using rose bengal was induced in the primary motor cortex or primary sensory cortex, and electrical stimulation was applied to the primary motor cortex, primary sensory cortex, or sencondary sensory cortex, respectively, in unilateral labyrinthectomized rats. Static vestibular symptoms including ocular movement and postural deficits, and expression of c-Fos protein in the medial vestibular nucleus (MVN) were measured. RESULTS: Lesion of the motor cortex produced a marked postural deficit with paralytic weakness in the hindlimb contralateral to UL. Number of spontaneous nystagmus in animals receiving cortical lesion was significantly increased 2, 6, and 12 hours after UL compared with animals being UL only. Lesion of the primary motor cortex or stimulation of the S2 sensory cortex decreased expression of c-Fos protein in MVN following UL compared with UL only group. Electrical stimulation of S2 sensory areas caused significant reduction of static vestibular symptoms and decreased expression of c-Fos protein in MVN 24 hours following UL. CONCLUSION: The present results suggest that cerebral cortex involves in recovery of static vestibular symptoms during vestibular compensation following UL.

Role of the Peripheral Vestibular End Organ in the Expression of c-Fos Protein in the Medial Vestibular Nucleus Following Occlusion of the Anterior Inferior Cerebellar Artery / 대한평형의학회지

BACKGROUND AND OBJECTIVES: The present study investigated the role of the peripheral vestibular end organ in vestibular symptoms and temporal changes in expression of c-Fos protein in the vestibular nuclei following anterior inferior cerebellar artery (AICA) occlusion using rats with unilateral or bilateral labyrinthectomy. MATERIALS AND METHODS: Expression of c-Fos protein in the vestibular nuclei was measured 2, 12, 24, and 48 hours after AICA occlusion. RESULTS: Unilateral AICA occlusion significantly induced expression of c-Fos protein bilaterally in the medial, inferior, superior, and lateral vestibular nuclei. Following AICA occlusion, the medial vestibular nucleus (MVN) showed the highest expression of c-Fos protein among the 4 vestibular nuclei. The expression of c-Fos protein was asymmetric between the bilateral MVN, showing higher expression in the MVN contralateral to the side of AICA occlusion compared to the ipsilateral MVN. The degree of asymmetry in c-Fos protein expression between the bilateral MVN peaked 12 hours after AICA occlusion. The expression of c-Fos protein gradually decreased 24 hours after AICA occlusion and returned to control levels 48 hours after AICA occlusion. Unilateral labyrinthectomy significantly decreased expression of c-Fos protein in the MVN ipsilateral to the side of labyrinthectomy following AICA occlusion. Moreover, bilateral labyrinthectomy significantly decreased expression of c-Fos protein in the bilateral MVN flowing AICA occlusion. CONCLUSION: These results suggest that afferent signals from the peripheral vestibular end organ are crucial to the expression of c-Fos protein in the MVN following AICA occlusion and that expression of c-Fos protein is sustained for 24 hours after AICA occlusion.

Quantification of Vestibulospinal Reflex Under the Stress Condition on Both Soleus Muscles / 대한평형의학회지

BACKGROUND AND OBJECTIVES: Vestibulospinal reflex (VSR), which is measured in static state, tends to be compensated prior to vestibule-ocular reflex. Therefore, by establishing method that enables to track and observe quantified VSR, the reliability of experiment is attempted to be increased. MATERIALS AND METHODS: On five SD Rats to measure electromyogram (EMG), electrodes, in the form of stranded cables composed of seven wires, are chronically implanted on both sides of the soleus muscles. Pre and post operative condition of sitting still, standing, and ladder step walking was compared before, and six and twenty four hours after a unilateral labyrinthectomy with quantified muscle activity in maximal voluntary activity. Simultaneously by using multi modality electric potential plus package, the muscle activity between the two legs was tracked and compared. RESULTS: In the sitting still position, the left/right soleus muscle activities were 25.7/26.0 microV before a unilateral labyrinthectomy which was changed after the surgery with the value of 23.1/8.1 microV and 23.4/14.3 microV when six and twenty four hours passed respectively. In the standing position, 92.8/124.0 microV of preoperative value was changed to 89.6/37.3 microV six hours after the unilateral labyrinthectomy, and it was 97.0/54.7 microV 24 hours after. The preoperative value in ladder step walking test was 56.2/86.0 microV, and postoperative ones were 54.9/21.2 microV and 55.7/38.0 microV after six and twenty four hours respectively. CONCLUSION: VSR assessment method by using quantitative EMG well reflects the process of vestibular compensation, and to maintain the tension of extensor muscles, ladder step walking test is shown to be useful.

Measuring the Behavioral Parameters of Mouse Following Unilateral Labyrinthectomy in Round Free Field Using an Infrared Lamp and a Simple Webcam Camera / 대한평형의학회지

BACKGROUND AND OBJECTIVES: In this research, movements of mouse after labyrinthectomy were analyzed to determine the degree of vestibular dysfunction and compensation. MATERIALS AND METHODS: By using an infrared lamp, mouse movements were recorded for 100 seconds in a dark room. The experimental area was manufactured as a circular space with a diameter of 60 cm. The movements of five mice labyrinthectomized on right side were observed and recorded at 3 hours, 9 hours and 120 hours after the operation, and also the ten mice of control group. RESULTS: The differences between the total moving distances and the rotating angle from the origin that set the center of round field between groups were analyzed with pictures of 1 frame per second. It is concluded that all 4 groups show significant differences between its mean rotation angle and total moving distances statistically. At 9 hours after right labyrinthectomy, mice tended to turn clockwise; but at 120 hours, there was no significant difference between clockwise and counter-clockwise rotation. CONCLUSION: Measuring the movement of mouse in round free field can be the proper method to determine the degree of vestibular dysfunction and vestibular compensation. This test was time-saving and cost-effective method.

Changes in the Gastrointestinal Motility following Unilateral Labyrinthectomy / 대한평형의학회지

BACKGROUND AND OBJECTIVES The temporal changes and the role of glutamate receptors in the recovery of vestibulogastrointestinal symptoms following unilateral labyrinthectomy (UL) were investigated in this study. Vestibulogastrointestinal symptoms were evaluated in terms of gastric emptying and intestinal transit. MATERIALS AND METHODS Expression of the c-Fos protein was observed in the solitary tract nucleus (STN) and rostral ventrolateral medullary nucleus (RVLM). These were measured at 0.5, 2, 6 and 24 h following UL in rats. RESULTS Gastric emptying and intestinal transit were significantly decreased for 6 h post UL and recovered to control levels within 24 h. Pretreatment of UL animals with MK-801 significantly increased the gastric emptying and intestinal transit. Bilateral labyrinthectomy significantly decreased the gastric emptying and intestinal transit compared to the intact labyrinthine animals but significantly increased when compared to UL animals. The expression of c-Fos protein was significantly increased in STN and RVLM compared to the control animals for 6 h post UL and recovered to control levels within 24 h. The expression was significantly decreased in animals that were pretreated with MK-801. CONCLUSION These results suggest that UL decreases the gastrointestinal motility, which recovers to control levels within 24 h post UL. Glutamate plays an important role in the recovery of vestibulogastrointestinal symptoms following UL.

Activation of Vestibular Neurons Projecting to Autonomic Brain Stem Nuclei Following Acute Hypotension in Rats

Extracellular regulated protein kinase1/2 (pERK1/2) is one of the major regulatory factors for transcription of the c-fos oncogene in neurons. The purpose of this study was to evaluate the expression of phosphorylated ERK1/2 within the vestibular nuclei (VN) of rats following acute arterial hypotension. Following the acute arterial hypotension induced by rapid hemorrhage, a significant number of pERK1/2-immunoreactive neurons appeared bilaterally in the caudal aspect of the medial and inferior VN. No labeling of pERK1/2 was observed in the lateral VN. The peak expression of pERK1/2 in these nuclei occurred within 5 min after hemorrhage. However, in bilaterally labyrinthectomized rats, the appearance of pERK1/2-immunoreactive neurons was eliminated in the VN. Western blot confirmed the effect of bilateral labyrinthectomy on pERK1/2 protein expression in the medial vestibular nucleus 5 min after hemorrhage. These results suggest that, following acute hypotension, afferent signals from the peripheral vestibular receptors are required for activation of ERK 1/2 in the VN.

Expression of Immediate-Early Gene Proteins by Transient Occlusion of Anterior Inferior Cerebellar Artery in Vestibular Nuclei of Sprague-Dawley Rats

BACKGROUND: Anterior cerebellar artery (AICA) occlusion results in vestibular dysfunctions because the AICA supplies the vestibular nuclei (VN) in the brain stem as well as the peripheral vestibular organs in the inner ear. The purpose of this study was to evaluate the expression of immediate-early gene products, a metabolic marker of neural excitation in neurons, by AICA occlusion in the VN of Sprague-Dawley rats. METHODS: After chloral hydrate anesthesia all animals were subjected to unilateral AICA occlusion by using a microsurgical clamp for 30 min to induce a transient ischemia. Unilateral labyrinthectomy was chemically undertaken to eliminate vestibular afferent activity. Immunohistochemical staining and image analysis for cFos, FosB, Krox-24, and JunB proteins were performed 2 hours after AICA occlusion. RESULTS: There was a high expression of cFos protein in the bilateral medial and inferior VN 2 hours after AICA occlusion. AICA occlusion induced minimal changes in cFos protein expression in the lateral and superior VN. Mild to moderate expressions of FosB and JunB protein in VN was observed 2 hours after ischemic injury of the brain stem and inner ear. On the contrary, the number of cFos and FosB immunoreactive neurons significantly decreased in the medial vestibular nucleus ipsilateral to the injured labyrinth 2 hours after AICA occlusion in the UL group. CONCLUSIONS: These results suggest that ischemic afferent activity from the peripheral vestibular apparatus is essential for the expression of immediate-early gene products in the medial and inferior VN of rats following AICA occlusion.

Immunohistochemical Identification of Phosphorylated Extracellular Signal-Regulated Kinase1/2 in Rat Vestibular Nuclei by Unilateral Labyrinthectomy

This study evaluated the expression of phosphorylated signal-regulated kinase1/2 (pERK1/2), which is one of the main factors regulating transcription of the cfos oncogene in neurons, in the vestibular nuclei of Sprague-Dawley rats following unilateral labyrinthectomy (UL). Surgical UL was performed to eliminate afferent signals from the peripheral vestibular receptors in the inner ear, under a surgical microscope, 2 hours after anesthesia. Significant numbers of pERK1/2 immunoreactive neurons were seen in the superior, medial, and inferior vestibular nuclei. There were more pERK1/2 immunoreactive cells in the vestibular nuclei contralateral than in the vestibular nuclei ipsilateral to the injured labyrinth, which resulted in significant asymmetric expression of pERK1/2 immunoreactive cells. Subsequently, the pERK1/2 immunoreactivity decreased rapidly, disappearing 90 min after labyrinthectomy. No pERK1/2 labeling was seen in the lateral vestibular nucleus. These results suggest that intracellular signal pathways for the activation of extracellular signal-regulated kinase in the vestibular nuclei are involved in lesion-neural plasticity in the vestibular system

Activation of cAMP-Response Element Binding Protein in the Brain Stem Nuclei during Vestibular Compensation in Unilateral Labyrinthectomizied Rats / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The p-CREB (phospholyated form of cAMP/calcium response element binding protein) was known to be one of transcription factors for immediate early genes in the brain stem nuclei. The purpose of this present study was to evaluate time-dependent expression of p-CREB and investigate the effect of MK801, non-competitive NMDA channel blocker, on p-CREB expression following unilateral labyrinthectomy (ULX). MATERIALS AND METHODS: Adult Sprague-Dalwey rats weighing 250-300 g were divided into a control group and an unilateral labyrinthetomy (ULX) group. The intraperitoneal injection of MK801 was administered either 30 min before or 24 hrs after ULX. The ABC immunohistochemical staining and digital image analysis system were used to measure the p-CREB expression in neuronal cells. RESULTS: The peak level of p-CREB expressions in 4 major vestibular nuclei was observed bilaterally with the other brain stem nuclei including reticular formation and olivary complex at 30 min following ULX. Thereafter, the p-CREB immunoreactivity in these nuclei was reduced rapidly to the control level for 6 hrs after ULX. Treatment of MK801 for 30 min preceding ULX decreased p-CREB immunoreactivity significantly in both the injured and intact sides of the 4 major vestibular nuclei with dose-dependent relationship. However, MK801 did not affect the change of p-CREB immunoreactivity in bilateral vestibular complex 24 hrs after ULX. CONCLUSION: These results suggest that cAMP/calcium response element binding protein plays an important role in the initial events of vestibular compensation in which its activity is in part regulated by NMDA receptor.

Effects of Deafferented Sensory Inputs on c-fos mRNA Expression in Medial Vestibular Nucleus of Rats Following Unilateral Labyrinthectomy / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Fos is a protein product of proto-oncogene c-fos, which is induced by various kinds of stimulations such as noxious, physiologic and electrical stimulations. In the vestibular system, there have been several evidences that c-fos was expressed in the brainstem vestibular nuclei during vestibular compensation following unilateral labyrinthectomy (ULX). In this study, the author evaluated the effect of deafferented sensory inputs on the c-fos mRNA expression in the medial vestibular nucleus of unilaterally labyrinthectomized rats. MATERIALS AND METHODS: Animals in the experimental group underwent tarsorraphy and cervical dorsal ganglionectomy to deprive them of visual and proprioceptive sensory inputs immediately after ULX, whereas the experimental group II did not receive any procedure after ULX. Expression of c-fos mRNA was demonstrated by in situ hybridization technique. All animals were sacrificed at 1, 3, 6, 9, 24, 48 hours after ULX and frozen sectioned tissues of brainstem were used in situ hybridization. RESULTS: Three hours after ULX, the expression of c- fos mRNA was increased in the dorsal portion of medial vestibular nucleus (dMVN) in both groups and after 6 hours of ULX, it was markedly reduced. In group I (deafferented), however, asymmetric expression was observed in 24 hours after the operation. In group II, the increased expression of c-fos mRNA in the ipsilateral dMVN continued until 9 hours after the operation and thereafter, the asymmetry of c-fos mRNA expressions between the ipsilateral and contralateral dMVN was decreased. CONCLUSION: These findings suggest that vision and proprioception influenced the expression of c-fos mRNA in the brainstem medial vestibular nucleus after ULX and corrected the asymmetric expression between the healthy and lesioned nuclei earlier than the deafferented group.

The Role of the Cerebellar Uvulonodulus on the Early Stage of Vestibular Compensation in Rats / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Many expeerimental evidences have beensupported that the vestibulocerebellum involved in recovery of vestibular compensation. The purpose of this study was to investigate effect of unilateral ablation of uvula and nodular lobes on early stage of vestibular compensation. MATERIALS AND METHODS: Adult Sprague-Dawley rats weighing 250~300 g were used and divided into control (CON) group receiving sham operation, unilateral labyrinthectomy (ULX) group, ULX plus left uvulonodulectomy (ULX+Lt-UNLX) group, and ULX plus right uvulonodulectomy (ULX+Rt-UNLX) group. UNLX was performed 1 hour following ULX. Spontaneous nystagmus (SN) and roll head tilt (RHT) were recorded for 3 days following ULX. Temporal change of c-Fos protein expression in the medial vestibular nuclei (MVN) was measured for 2 days following ULX. RESULTS: There were observed SN with contralateral direction to injured labyrinth and RHT toward ipsilateral side with flexion of ipsilateral limb and extenstion of contralateral one just after ULX. There was significant increase in SN frequency of ULX+Rt-UNLX group compared with that of ULX group. In addition, ULX+Rt-UNLX group resulted in severe postural asymmetry. ULX elicited prominent expression of c-Fos protein in contralateral MVN 2 hours but in ipsilateral one 6, 24 hours after ULX, respectively. In contrast, number of c-Fos positive neurons was higher in contralateral MVN. 24 hours after ULX higher expression of c-Fos protein in contralteral MVN was still remained in ULX+Rt-UNLX group but that in ipsilateral MVN was observed in ULX+Lt-UNLX group. CONCLUSION: These results suggest that UNLX have a different effect on the early stage of vestibular compensatory process and the uvulonodulus serves the restoration of balance between intervestibular nuclear activities after ULX by inhibition of vestibular nuclear complex through nhibitory Purkinje system.

Effects of MK801 on Neuronal Activity of the Contralateral Medial Vestibular Nuclei Following Unilateral Labyrinthectomy in Rats / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Several lines of evidence suggest that recovery of symptoms following unilateral labyrinthectomy (ULX) is due to the restoration of neuronal activity in the ipsilateral vestibular nuclei, leading to the reestablishment of bilateral symmetry in the resting neuronal activity. Effects of dizocilpine maleate (MK801), a non-competitive NMDA receptor antagonist, on vestibular compensation following unilateral labyrinthectomy (ULX) were investigated in adult Sprague-Dawley rats. MAERIAL AND METHODS: Responses of spontaneous nystagmus and neuronal activity of the contralateral medial vestibular nuclei (MVN) to labyrinthectomy were recorded in course of time after intraperitoneal injection of MK801. RESULT: Spontaneous nystagmus decreased gradually with time, but recovery of the nystagmus was aggravated 2 to 4 hours after administration of MK801 (p<0.05). In the labyrinthine intact rats, MK801 treatment significantly increased resting activity of type I and II in MVN compared with non-treated rats, and the effect of MK801 on neuronal activity was more prominent in the type I neurons than in the type II neurons. After 6 hours of ULX, the activities of type I and II neurons were decreased compared with labyrinthine intact rats, and type II neurons showed higher activity than the type I neurons. MK801 treated ULX rats showed higher resting activity in the type I and II neurons than in the labyrinthine intact rats or ULX rats, but lower resting activity than the MK801 treated labyrinthine intact rats. In the neuronal activity induced by sinusoidal rotation, gain was the highest in the MK801 treated ULX rats among the 4 experimental groups, and sensitivity was decreased in the type I & II neurons by treatment of MK801. CONCLUSION: These results suggest that MK801 deteriorates asymmetry of the resting activity in the bilateral MVN by inhibition of cerebellar Purkinje system inhibiting the intact MVN, which results in decompensation of the vestibular function following ULX.

Spontaneous, Positional, Positioning and Post Head Shaking Nystagmus in Unilaterally Labyrinthectomized Cats / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Unilateral vestibular dysfunction evokes many bothersome symptoms such as nausea, vomiting, vertigo, ataxia, and positional change. We attempted to understand the vestibular signs after a loss of unilateral vestibular function. MATERIALS & METHOD: We evaluated the serial changes of eye movements and body posture after unilateral labyrinthectomy which was performed on five cats. Data obtained from three of these cats. The eye movements were measured in vertical, horizontal and torsional planes using magnetic search coils, with eyes open in light and eyes open in darkness. The eye movements were recorded with head in neutral, tilted, hanging, and Dix-Hallpike position, and after head was shaken. RESULTS: 1) Spontaneous nystagmus was present for the first three days. 2) Head tilting positional nystagmus was present only on the first day after the operation. Head hanging position produced nystagmus with high slow phase eye velocity for 4 weeks. 3) Positioning nystagmus was recorded for 4 weeks and it was more prominent when labyrinthectomized ear was undermost. 4) Head shaking nystagmus around the pitch and roll axis was evoked within one week, but in the yaw axis it persisted for 4 weeks. When the cat was tilted to the lesion side, the intensitiy of positional and positioning nystagmus was stronger. CONCLUSION: Unusual positions such as head hanging and Dix-Hallpike position evoked prolonged nystagmus. Head shaking in the yaw axis could be used on a long term basis to understand unilateral vestibular dysfunction.

Temporal changes in neuronal activity of the bilateral medial vestibular nuclei following unilateral labyrinthectomy in rats

To investigate the changes in the responses of vestibular neurons with time during vestibular compensation, the resting activity and dynamic responses of type I and II neurons in the medial vestibular nuclei to sinusoidal angular acceleration were recorded following unilateral labyrinthectomy (ULX) in Sprague-Dawley rats. The unitary extracellular neuronal activity was recorded from the bilateral medial vestibular nuclei with stainless steel microelectrodes of 3~5 MOMEGA before ULX, and 6, 24, 48, 72 hours, and I week after ULX under pentobarbital sodium anesthesia (30 mg/kg, i.p.). Gain (spikes/s/deg/s) and phase (in degrees) were determined from the neuronal activity induced by sinusoidal head rotation with 0.05, 0.1, 0.2, and 0.4 Hz. The mean resting activity before ULX was 16.7+/-8.6 spikes/s in type I neurons (n=67, M+-SD) and 14.5+/-8.4 spikes/s in type II neurons (n=43). The activities of ipsilateral type I and contralateral type 11 neurons to the lesion side decreased markedly till 24 hr post-op, and a significant difference between ipsilateral and contralateral type I neurons sustained till 24 hr post-op. The gain at 4 different frequencies of sinusoidal rotation was depressed in all neurons till 6 or 24 hr post-op and then increased with time. The rate of decrease in gain was more prominent in ipsilateral type I and contralateral type 11 neurons immediately after ULX. Although the gain of those neurons increased gradually after 24 hours, it remained below normal levels. The phase was significantly advanced in all neurons following ULX. These results suggest that a depression of activities in ipsilateral type I and contralateral type II neurons is closely related with the occurrence of vestibular symptoms and restoration of activities in those neurons ameliorates the vestibular symptoms.

c-fos Expression in Medial Vestibular Nucleus of Guinea Pigs After Unilateral Labyrinthectomy / 听力学及言语疾病杂志

Objective To investigate the c-fos ex pr ession in guinea pigs' medial vestibular neuleus (MVN) following unilateral laby rinthectomy (UL). Methods Twenty-seven SCO guinea pigs were randomly divide d into nine groups, three in each group. After resection of right labyrinth,th e immunohistological staining of c-fos was performed. Fos-like immunoreactivity (FLI) was analyzed at fifteen minutes, and 1?2?6?8?12 and 24 h, and 2 and 7 days after UL. Results Results showed no Fos expression in the control g roup. By contrast, Fos was consistently induced in the UL guinea pigs. Asymmetri cal labeling was found in the bilateral medial vestibular nucleus, with more Fos -like neurons in the ipsilateral MVN of the lesioned side than that in the contr alateral MVN(P

Studies on the Vestibular Compensation after Contralateral Labyrinthectomy in Unilateral Labyrinthectomized Rats / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Vestibular compensation is a process of behavioral recovery following unilateral labyrinthectomy (ULX). The neural plasticity in vestibular compensation was assessed by observing changes of behavioral response and c-Fos expression following contralateral labyrinthectomy (second labyrinthectomy) in ULX rats. MATERIAL AND METHODS: Contrala-teral labyrinthectomy was performed 2 weeks after ULX in Sprague-Dawley rats, each weighing 250-300 gm. Changes of spontaneous nystagmus, head tilt, and c-Fos expression in the medial vestibular nucleus (MVN) and nucleus prepositus hypoglossi (PrH) were measured. RESULT: In ULX, spontaneous nystagmus with the slow phase directed to the lesion side was 3.5+/-0.5 beats/sec and head tilt deviated to the lesion side was 71+/-16 degrees just after ULX. Spontaneous nystagmus disappeared within 72 hours, but head tilt was maintained at 28+/-8 degrees until 2 weeks after ULX. The number of c-Fos proteins 2 hours after ULX was 81+/-25 and 212+/-63 in MVN of the lesion side and the intact side, respectively. And PrH showed 136+/-37 in the lesion side and 94+/-19 in the intact side, which was opposite of MVN in spatial expression of c-Fos. In second labyrinthectomy, direction of spontaneous nystagmus and head tilt was opposite to the first ULX and their decrement was faster. c-Fos was expressed more in the MVN of the first labyrinthectomized side than in the second one and PrH showed the opposite pattern to MVN, which was opposite to the first ULX in spatial expression. CONCLUSION: These results suggest that recovery of vestibuloocular reflex in vestibular compensation is accomplished by restoration of neuronal activity in the central nervous system including MVN and PrH.